A key Information and Communication Technology (ICT) component for realizing smart communities is environmentally friendly mass-storage technology capable of reducing energy consumption and saving space. To achieve such a capability, the storage density of magnetic recording, which is a mainstream storage technique, has been improved remarkably as a result of recent progresses in fundamental research as well as micro- and nano-fabrication technology.
Three-dimensional magnetic recording has been proposed as a way to increase magnetic storage density. In comparison with a conventional magnetic medium having only a single recording layer, a three-dimensional magnetic storage medium has multiple recording layers allowing the storage density per unit area to be increased in accordance with the number of layers. In a three-dimensional magnetic storage medium the recording layer is selected by using ferromagnetic resonance when reading or writing. Since each recording layer has a different ferromagnetic resonance frequency, a desired layer can be selected when reading or writing by applying a high-frequency magnetic field which causes ferromagnetic resonance only in the desired layer.